“How will they make money?” is the wrong question

I think Ev Williams captured this best in his answer to a related question on Quora:

Having a large number of users and the inability to monetize them is a non-existent problem. People talk about it all the time, but it doesn’t really happen—at least it doesn’t happen in today’s world. I’m not even sure it ever did.

In all of these cases, the primary challenge with building a large consumer company is not “how will you make money,” but  “how do you get to be a long-standing durable network and define a new set of behaviors or verbs?”  Once you can do that, it’s very likely you will be able to monetize at significant scale.